The invitations to the April 4 event, which were sent to members of the media this evening via e-mail, reveal only that the company will be showing off its "new home on Android."

Already, rumors are beginning to fly about what Facebook might announce.

TechCrunch reported that Facebook will unveil phone software based on Google's Android operating system. The software will have "extra Facebook functionality built in." According to the report, the phone software will run on hardware made by HTC.

HTC, a Taiwanese phone maker, released The Status in 2011, an Android phone that had Facebook branding and specialized Facebook software. The phone wasn't marketed by Facebook and received poor reviews. The company recently announced its new HTC One Android phone.

Amazon has taken a similar route, creating its own version of Android software to run on its Kindle Fire. It places Amazon's services front and center.

Facebook has been rumored to be working on a phone of its own for a number of months now. However, while Facebook CEO Mark Zuckerberg has said the company is focused on mobile and is a mobile company, he has denied the existence of plans for a "Facebook phone."

"We want to support an ecosystem where other apps can build on top of Facebook," Zuckberg said on an earnings call last year. "There are a lot of things you can build in other operating systems, as well, that aren't really taking, that aren't really like building out a whole phone, which wouldn't make much sense for us to do."